Patent GB-126755-A (GB)
Title: Improvements in or relating to Electric Selective Switching Systems and Apparatus.
IPC: H01H67/06
Filed: 1918-02-14
Abstract: 126,755. International Electric Co., and Baldock, F. R. Feb. 14, 1918. Automatic exchange systems and apparatus.-In an automatic switch, particularly for automatic exchange telephone' systems of the two-wire type, the actuating-magnets serve as relays to make the necessary circuit changes and as feeding-coils for the microphone current. The invention is described as applied to a selector in which the wipers are moved in one direction only to select a group of lines and then a line within the group. Construction of selector. The wipers 11, 12, 13 are carried by a plate 8 secured to a spindle 5 mounted in a skeleton framework 1, 2 formed of stamped parts. The actuating-magnets 20, 21, mounted on brackets 22, 23, act through pawls 27, 44 on the ratchet wheels 28, 45 to move the wipers through large and small steps, corresponding to the first and second digits of the wanted line. A release magnet 24 controls the detent 53. The bank contacts are numbered in the .first group as 1, 11, 12 - - 18, 19, 10; in the second group as 2, 21, 22 - - 28, 29, 20, and so on, certain lines having one digit only. The magnet 20 controls groups of contacts 30, 41 and the magnet 21 similarly controls contacts 49. The contacts 30 are operated at each energization of the magnet 20 by an auxiliary armature 29, while the contacts 41 are operated, after a delay imposed by any suitable timing device such as a dash-pot or friction governor, by a spring-controlled arm 40 carrying a pin 35 arranged to co-operate with the bent ends of two springs 31, 32 carried by the main armature 26. The arrangement is such that when the armature is attracted, the pin 35 escapes from the spring 31 and is held by the spring 32, which releases it when the armature is retracted. The arm 40 carried a projection 42 which disengages the pawl 27 so that further interruptions of the circuit of magnet 20 are without effect on the ratchet wheel 28. The arm 40 is restored by a V-shaped part 60 when the switch is released. Some structural modifications are described in the Provisional Specification. Operation of system, Fig. 6. Besides the actuating and release magnets 20, 21, 24 of the switch, each subscriber's line is provided with a cut-off relay 70 and a ringing-relay 71. When the subscriber removes his receiver, the aotuating- magnet 20 is energized over the calling-line A and contact 75, 76, and closes contact 81, 82 to mark the calling-line busy. The first set of line interruptions causes the magnet 20 to move the wipers to the group of contacts containing the wanted line. At the end of the first impulse, the arm 40 moves slowly towards the set of contacts 41, and, when all the impulses for the first digit have been received, throws the pawl 27 out of action and, by shifting contacts 41, makes the necessary changes in the connexions, including the removal of the short circuit at contact 75, 76 around the magnet 21. The magnet 21 responds to the second set of impulses and moves the wipers to the terminals of the wanted line. Busy test, signal, and release. If the wanted line is busy, its test terminal is connected to battery so that the release magnet 24 is at once energized over contacts 90, 89 (closed on the first movement of the arm 48), 91, 92, test wiper 13, and test terminal. The release magnet 42 releases slowly and connects a busy tone over contacts 55, 56 to the calling-line. Ringing-current. If the wanted line is free, the arm 48 moves far enough to operate the springs 49, whereby the cut-off relay of the wanted line is energized over the test wiper 13, contacts 92, 93, and battery, and the ringing- relay 71 is energised over contacts 51, 95, 94, the circuit of the motor driving the ringing- interrupter having been previously closed at contacts 86, 87. When the called subscriber replies, the increase in the current in the magnet 21 causes this to attract its auxiliary armature, thereby opening contact 50, 51 in the circuit of the ringing-relay. Microphone current and release. Microphone current is supplied to both lines in parallel over the magnets 20, 21, the connexion being released when both subscribers replace their receivers, the circuit ; of the release magnet 24 being completed over contacts 85, 84, 80, and 81. Conference calling. A number of subscriber's lines may be multipled on a single set of bank contacts so that these lines may be used for conference purposes.